**Core Concept**
The question is testing the knowledge of preservatives used in medical sutures, specifically catgut suture. Catgut suture is a type of absorbable suture made from the intestines of animals, typically sheep. Preservatives are added to the suture to prevent bacterial growth and extend shelf life.

**Why the Correct Answer is Right**
The correct answer is likely **B. Glyoxal**, a type of aldehyde preservative. Glyoxal is commonly used as a preservative for catgut sutures due to its ability to inhibit the growth of bacteria, fungi, and yeast. When catgut suture is exposed to air, it undergoes oxidation, which can lead to bacterial growth. Glyoxal prevents this oxidation reaction, thereby preserving the suture.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not specified, so it cannot be evaluated.
* **Option C:** This option is also not specified, so it cannot be evaluated.
* **Option D:** This option is not a known preservative for catgut suture.

**Clinical Pearl / High-Yield Fact**
It's essential to note that catgut sutures are absorbable and should not be used in areas where there is high risk of infection or tissue breakdown. The use of glyoxal as a preservative does not make the suture non-absorbable.

**Correct Answer:** B. Glyoxal